Polyimides resins having excellent film properties such as heat resistance, mechanical properties and electric properties have been conventionally used for an interlayer insulating film or surface protection film in a semiconductor device. However, when using a non-photosensitive polyimide resin as an interlayer insulating film or the like, a patterning process requires the use of a positive resist, which leads to additional processes such as etching and resist removal, resulting in a more complex manufacturing process. There has been, therefore, investigated the use of a photosensitive polyimide resin exhibiting good photo-sensitivity. It can be used as an interlayer insulating film or the like to eliminate the use of a positive resist in the patterning process, resulting in a simple manufacturing process. Examples of such a photosensitive polyimide resin composition include positive photosensitive resin compositions consisting of a polyamic acid, an aromatic bisazide compound and an amine compound described in Patent document 1. However, a developing step in a patterning process of a photosensitive polyimide resin requires an organic solvent such as N-methyl-2-pyrrolidone and ethanol, which may lead to problems related to safety or environmental impact.
Thus, there has been recently developed a positive photosensitive resin composition as a patterning material which can be developed with an aqueous alkaline solution such as an aqueous solution of tetramethylammonium hydroxide (TMAH) used in a fine patterning process for a semiconductor. For example, Patent Document 2 has described a non-chemical amplification type of positive photosensitive resin composition consisting of a polybenzoxazole precursor and a diazoquinone compound as a photosensitizing agent. Non-Patent Document 1 has described a non-chemical amplification type of positive photosensitive resin composition consisting of a polybenzoxazole precursor and a 1,2-naphthoquinonediazide-5-sulfonate. In addition, Non-Patent Document 2 has described a chemical amplification type of positive photosensitive resin composition consisting of a polybenzoxazole precursor protected by a group being decomposed by an acid and a photoacid generator.
In such a photosensitive resin composition, its structure is changed by heating to form a benzoxazole ring, resulting in good heat resistance and electric properties. For example, a polybenzoxazole precursor described in Non-Patent Document 1 forms a benzoxazole ring by heating after development with an alkaline solution as shown in reaction equations A and A′. Since the benzoxazole ring is a stable structure, an interlayer insulating film or surface protection film prepared using a photosensitive composition consisting of the polybenzoxazole precursor exhibits excellent film properties such as heat resistance, mechanical properties and electric properties.
    Patent Document 1: Japanese published examined application 3-36861.    Patent Document 2: Japanese published examined application 1-46862.    Non-Patent Document 1: M. Ueda et al., Journal of Photopolymer Science and Technology, Vol.16(2), pp. 237 to 242 (2003).    Non-Patent Document 2: K. Ebara et al., Journal of Photopolymer Science and Technology, Vol 16(2), pp. 287 to 292 (2003).